Remove a method that was just replacing direct access to a member.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210598 91177308-0d34-0410-b5e6-96231b3b80d8
Move AArch64InstrInfo to AArch64Subtarget.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210599 91177308-0d34-0410-b5e6-96231b3b80d8